WO2009125119A1

WO2009125119A1 - Method and facility for determining the interfacial tension between two liquids, and method of screening various liquids

Info

Publication number: WO2009125119A1
Application number: PCT/FR2009/050498
Authority: WO
Inventors: Annie Colin; Pierre Guillot; Armand Ajdari
Original assignee: Rhodia Operations; Universite Bordeaux I
Priority date: 2008-03-25
Filing date: 2009-03-24
Publication date: 2009-10-15
Also published as: JP5385370B2; EP2265924B1; JP2011515693A; KR20100132970A; FR2929403B1; EP2265924A1; US8613217B2; FR2929403A1; US20110197664A1

Abstract

According to this method: an internal liquid (Li) is made to flow through an internal flow member (2) and an external liquid (Le) is made to flow through an external flow member (4); conditions are firstly set up so that either droplets (G) of the internal liquid are formed in the external liquid, or a continuous jet of the internal liquid is formed in the external liquid; the flow rate of at least one of the two liquids is varied; a pair of transition liquid flow rate values are identified, from which either a continuous jet of the internal liquid is then formed in the external liquid or droplets of the internal liquid are then formed in the external liquid; and said value of the interfacial tension between these two liquids is deduced therefrom.

Description

METHOD AND APPARATUS FOR DETERMINING THE INTERFACIAL VOLTAGE BETWEEN TWO LIQUIDS, AND METHOD OF SCREENING

DIFFERENT LIQUIDS

The present invention relates to a method for determining the interfacial tension between two liquids, an installation for carrying out this method, and a screening method comprising such a determination method.

When two immiscible liquids are brought into contact with each other, it is necessary to provide energy to increase their contact surface. If this energy is low, the flow of these two liquids is realized in the form of two respective jets. If we gradually increase this energy, these two liquids eventually form drops. The energy per unit area, which should be provided for the formation of such drops, is called the interfacial tension between the two liquids considered.

Knowledge of this interfacial tension value is of great importance in many technological sectors. Non-limiting examples include chemical processes, ink jet printing, spray atomization, emulsification processes, and polymer extrusion.

Several methods are already known in the state of the art for determining the value of this interfacial tension.

A first solution, called the weighed drop method, consists in collecting a determined number of drops in a container, from a capillary. By weighing the container, the average weight of each drop is then deduced, and the interfacial tension is then calculated from the value of this weight, as well as from the radius of the capillary used.

An alternative solution, called the rotating drop, consists of pouring a drop into a container and then rotating it under the effect of centrifugal force. From different parameters, such as in particular the shape adopted by the drop during its rotation, the value of the interfacial tension is deduced.

These known solutions, however, have certain disadvantages. Thus, they often prove tedious to implement. In addition, each method of determination is limited to a relatively narrow range of measures.

In this respect, the weigh drop method is more particularly intended for the study of liquids with high interfacial tensions, typically greater than 5 mN / m. On the other hand, the rotary drop method is suitable only for very low values of interfacial tensions, typically less than 0.1 mN / m.

That being said, the invention aims to remedy these various disadvantages. It aims in particular to provide a method for determining, reliably and simply, the interfacial tension value between two liquids. It also aims to provide such a method, which can be implemented for a wide range of interfacial tensions. Finally, it aims to propose such a method, which is capable of allowing the determination of the interfacial tension for many pairs of liquids, in particular by virtue of a rapid change in the composition of the latter.

For this purpose, it relates to a method for determining at least one interfacial tension value between two liquids, comprising the following steps:

a first liquid, said internal liquid, is made to flow in an internal flow member, and a second liquid, said external liquid, into an external flow member, the internal and external flow members respectively. being coaxial, and the inner member opening into the internal volume of the outer flow member;

first of all, the conditions are such that, downstream of the outlet of the internal flow member in the external flow member, it is formed,

. i) drops of the internal liquid in a carrier phase P formed by the external liquid,

. ii) a continuous stream of the inner liquid in the outer liquid;

the flow rate of at least one of the two liquids is varied;

a pair of liquid flow rate values, referred to as transition values, are identified from which . i) a continuous stream of the internal liquid is now formed in the external liquid;

. ii) drops of the internal liquid are now formed in the external liquid; and - said interfacial tension value between these two liquids is deduced therefrom.

According to other characteristics:

the diameter of the internal flow member is between 10 micrometers and 2 millimeters, in particular between 10 and 200 micrometers, while the diameter of the external flow member is between 50 micrometers and 4 millimeters, preferably between 100 and 500 micrometers;

- the ratio between the diameter of the outer flow member and the diameter of the inner flow member is between 1, 2 and 10, preferably between 1, 5 and 5; the two liquids are discharged at flow rates of between 1 microliter per hour and 100 ml per hour, preferably between 10 and 10,000 microliters per hour;

the flow rate, said outside, of the external liquid is fixed and the flow, called the internal flow, of the internal liquid is varied; the value of the interfacial tension is deduced from the fixed flow rate of the external liquid, the flow rate of the internal liquid, the diameter of the outer capillary, as well as the viscosities of the inner and outer liquids;

to deduce this value of interfacial tension, the equation is used:

Kax ⁱ E (x, λ) = CF (x, λ) where

E (x, λ) = -Ax + (8 - 4 / T ¹ ) x ³ + 4 (/ L ^"1 - 1) x ⁵ , F (x, λ) = x ⁴ (4 - / T ¹ + 4 ln (jc)) + x ⁶ (-8 + 4 / T ¹ ) +

a- f ⁺ * ^* %> ^•

Ka = -, with

7

_AP =. ¹²⁸ ^ a πDS 'X -x ¹ )

several interfacial tension values are determined between the same two liquids, successively fixing different values of external flow, then, for each of these values thus fixed, by varying the internal flow rate values;

a surfactant is added to the two liquids, the drop formation time is varied, several interfacial tension values are determined between these two same liquids, relating to different drop formation times, a curve representing the variation of this value of interfacial tension as a function of the drop formation time, and a characteristic time of the surfactant is identified, corresponding to the transition between an area where the interfacial tension value is substantially constant as a function of the formation time, and an adjacent zone , where this interfacial tension value increases as this formation time decreases;

the existence of drops or the existence of a jet is identified by placing a laser emitter and a photodiode on either side of the external flow member, downstream of the outlet of the organ of internal flow. The invention also relates to an installation for implementing the method as above, comprising:

an inner flow member and a coaxial outer flow member, the inner flow member opening into the internal volume of the outer flow member;

means for supplying two liquids, respectively in the two flow members;

means for varying the flow rate of at least one of the liquids; and

means for observing the flow of the first liquid in the second liquid.

Finally, the subject of the invention is a method for screening different pairs of liquid, in which these different pairs of liquid are prepared, determining at least one interfacial tension value relative to each of these pairs of liquid, according to the method described above. above, and at least one preferred pair of liquids is identified among said plurality of liquid pairs.

According to other characteristics:

the different pairs of liquid are prepared by adding at least one substance to at least one liquid, this substance being in particular a surfactant and / or a polymer and / or a solid particle; and the different pairs of liquid are prepared by modifying at least one condition of at least one liquid, in particular the pH and / or the temperature and / or the pressure.

The invention is described below, with reference to the accompanying drawings, given solely by way of non-limiting examples, in which: FIG. 1 is a side view, illustrating an installation allowing the implementation of a method of determination of the interfacial tension between two liquids according to the invention;

Figures 2, 4 and 5 are side views, similar to Figure 1, illustrating different stages of implementation of this method; FIG. 3 is a graph illustrating the variations of the signal of a photodiode as a function of time,

Figures 6 and 8 are curves, illustrating different values of transition rates, obtained according to the invention; and FIG. 7 is a graph illustrating the variation of the surface tension as a function of the drop formation time.

The installation according to the invention, which is illustrated in Figure 1, comprises two flow members, respectively inner 2 and outer 4. These flow members are for example capillaries, made in particular of glass, treated glass , PTFE, or plastic.

These two capillaries 2 and 4 are advantageously coaxial, and thus have a common principal axis noted A. D _{1 also} denotes the outer diameter of the inner capillary 2, namely that this diameter includes the walls of the capillaries. It is further noted _e D the internal diameter of the capillary 4 outside, that this value of diameter not however includes the walls of the capillary 4.

Advantageously, D ₁ is between 10 microns (or microns) and 2 millimeters, preferably between 10 microns and 200 microns, while D _e is between 50 microns and 4 millimeters, preferably between 100 microns and 500 microns. In addition, the ratio D _e / D is advantageously between 1.2 and 10, preferably between 1.5 and 5.

The outlet of the inner capillary 2 is noted in the internal volume of the outer capillary 4. Immediately downstream of this outlet 2 ', there is provided a laser emitter 6, a first side of the capillary 4, which is associated with a photodiode 8, placed opposite this transmitter 6. As will be seen in the following, this transmitter and this photodiode are capable of delivering a signal, to obtain information on the formation of drops and on the frequency of this training.

The installation described above, with reference to Figure 1, allows the implementation of a method according to the invention for determining the interfacial tension between two liquids. For this purpose, the capillaries 2 and 4 are placed in communication with means for feeding two immiscible liquids to be tested. These supply means, which are of conventional type, are not shown in the figures. In the usual way, it may for example be syringe shoots and microfluidic connectors.

First, it is necessary to fix the external flow, denoted Q _e (1), of the liquid flowing in the outer capillary. Advantageously, this external flow rate value is between 1 microliter / hour and 100 ml / hour, preferably between 10 microliters / hour and 10,000 microliters / hour. In addition, the external flow, denoted Q ₁ , of the liquid LJ flowing in the inner capillary is given a very low value. Under these conditions, bringing these two immiscible liquids into contact leads to the formation of drops G, constituted by the internal liquid, in a carrier phase P formed by the external liquid (see FIG. 2).

Then, for this same external flow rate Q _e (1), the flow rate value Q ₁ is progressively increased, according to a predetermined function Q ₁ = f (t) as a function of time. The signal emitted by the photodiode is then observed as a function of time.

At the beginning of the flow of the two liquids, corresponding to the formation of drops, the signal is periodic, namely that it oscillates between two values, respectively Si and S ₂ (see Figure 3). The value Si corresponds to the position in which the laser and the photodiode are separated by both the internal liquid and the external liquid (FIG. 4), while the signal S ₂ corresponds to the position for which this laser and this photodiode are only separated by the external liquid (Figure 2).

Above a certain flow rate value Q ₁ , it is noted that the drops initially produced are replaced by a continuous jet J of the internal liquid in the external liquid (FIG. 5). From the moment when this threshold value is reached, the signal emitted by the photodiode stabilizes at the value s <ι, since the laser and the photodiode are permanently separated by both the internal liquid and the external liquid.

From the curve of Figure 3, we identify the moment, noted t (1), corresponding to the appearance of the continuous stream. Since, as seen above, the variation of flow Q ₁ is known as a function of time, it is possible to access the flow rate value Q ₁ (I) corresponding to this moment t (1) of formation of the jet. Knowing the value of the external flow Q _e (1), as well as the value of the internal flow Q ₁ (I) for which appears the continuous stream, we can deduce the value of the interfacial tension γ {\) between the two liquids. For this purpose, the following equation is used: Kax ⁱ E (x, λ) = CF (x, λ), where

E (x, λ) = -Ax + (8 - 4 / T ¹ ) x ³ + 4 (/ L ^"1 - 1) x ⁵ , F (x, λ) = x ⁴ (4 - / T ¹ + 4 ln (x)) + x ⁶ (-8 + 4 / T ¹ ) +

i. a4 ^{i + r '} § ^h and

at-\

From \, λ ^{~ ι} + a- \

The resolution of equation (1) above gives access to the value of Ka, then to that of γ using the following equation:

Ka = -, with

Y

AP = ¹²⁸ ^ a πD _e ^A (\ -x ² )

As can be deduced from the foregoing, this interfacial tension value can be deduced by knowing only the values of the fixed external liquid flow rate Qe, the internal liquid flow of transition Qi, the diameter De of the outer capillary, as well as the viscosities n , and n _e inner and outer liquids. This value can be known in a simple and fast way.

The operation described above can be repeated by setting each time the external flow rate Q _e at different values, denoted by Q _e (2) at Û2 (n). This allows access to corresponding internal flow rate values, denoted by Q, (2) to Q ₁ (n), for which the transition between the drops and the jet takes place. For each group of values Q ₁ (J) and Q _e (j), where j varies from 1 to n, it is also possible to deduce n interfacial tension values denoted by ((1) to ((n). Internal flow values

Q ₁ are typically between 1 microliter / hour and 100 ml / hour, especially between 10 microliters / hour and 10,000 microliters / hour.

In addition, in Figure 6, there is shown the different values of Q _e and Q ₁ , firstly fixed, and secondly determined according to the steps above. The Curve C connects the different internally determined flow values determined experimentally. Thus, to the left of this curve, the values of internal and external flow are such that the flow of two liquids form drops of the inner liquid in the external liquid. On the other hand, to the right of this curve, this flow leads to the formation of a continuous stream of the internal liquid in the external liquid. Obtaining this curve C is interesting because it makes it possible to check the uncertainty on the measurement.

As a variant, for a fixed external flow rate, it is possible to choose a very high initial internal flow rate, such that bringing the two liquids into contact leads to the formation of a jet. In other words, it is initially right of the curve C of Figure 6, and not left as in the first embodiment.

Then, this value of internal flow is gradually decreased until drops are obtained. In a manner similar to what has been described above, the internal flow rate sought corresponds to that for which the transition between jet and drops is identified, and not between drops and jet, as in the first embodiment illustrated in FIG. .

As a variant, it is possible to envisage setting, not the external flow rate, but the internal flow rate so that, in this case, the external flow rate is then varied. This may be of interest for reducing measurement errors, in particular by first carrying out a first series of measurements with fixed external flow rate, and then a second series with fixed internal flow rate, for the same liquids. It is then possible, advantageously, to average the values obtained during these two series of measurements. According to an advantageous variant of the invention, it is possible to carry out a screening of different pairs of liquid, by using the method of determining surface tension, as described above.

For this purpose, the flow capillary 2 and 4 are connected with means for adding at least one substance in at least one liquid, and / or with means making it possible to modify the conditions of the flow of water. at least one of these liquids. The adding means make it possible to add, to one and / or the other of the liquids, different types of substances such as a surfactant, a polymer, solid particles, salts, acids, or bases. The means of For example, changes in the flow conditions may vary the pH, the temperature or the pressure.

A pair of so-called base liquids is then prepared, the surface tension of which is determined according to the method described above. Then, the base pair is modified by adding at least one substance in at least one liquid, and / or modifying at least one condition of at least one of these base liquids.

The different surface tensions relating to the different pairs of liquid thus prepared are then determined. Finally, one or more preferred pairs of liquids, for example those having the lowest surface tension, are determined.

FIG. 7 illustrates an advantageous variant of the invention, in which different values of interfacial tension are measured as a function of the rate of formation of the drops. As will be seen in what follows, this makes it possible to determine the rate of adsorption of a surfactant at the interface between the liquids, namely the dynamic interfacial tension.

The same installation as that described in FIG. 1 is used. It should however be noted that a surfactant is flowed out, the properties of which it is desired to determine. This surfactant is added, in the usual way, to one and / or the other of the liquids.

In the first step of this embodiment, it is necessary to set an external flow rate Q _e at a very low value, denoted Q _e (1). In this way, this makes it possible to ensure that the surfactant has the necessary time to adsorb at the interface between the two liquids. Then, the inner liquid is run at a very low initial flow rate, which is gradually increased according to the procedure described above. We denote Q ₁ (I) the value of internal flow, beyond which the drops are transformed into a continuous stream.

We also note ω - _\ the frequency of formation of these drops, which is very low because of the very low flow rate value Q _e (1). This formation frequency is measured for example by the laser emitter 6, associated with the photodiode

8. Finally, according to equation (1) above, the value γ 1 of the interfacial tension is calculated from the values Q _e (1) and Q ₁ (I) above. In a second step, the external flow rate is set to a value Q _e (2) greater than that Q _e (1) above. Consequently, the frequency ω ₂ of formation of the drops will be greater than that ω 1, mentioned above. Then, similarly to the first step, the flow rate Q ₁ is varied, until a value Q (2) corresponding to the transition between the drops and the continuous jet is identified. This makes it possible to obtain a second interfacial tension value, denoted γ2.

These two steps are repeated, iteratively, for n flow values, which makes it possible to obtain n drop formation frequency values, as well as n interfacial tension values. Then, in FIG. 7, the variation of the interfacial tension γ is plotted as a function of the drop formation time t, which corresponds to the inverse of the frequency ω. This figure shows the values U, k, t _n- i, t _n , as well as

It can be seen that the curve C thus obtained is divided into two main zones. There is thus a first zone I, corresponding to high formation times and therefore low production frequencies, for which the value of the interfacial tension γ is substantially constant. In other words, in this portion of the curve, the drops are formed sufficiently slowly, to allow the surfactant to adsorb at the interface between the two liquids.

Then there is a zone II, corresponding to higher training frequencies, namely shorter formation times. As we approach the minimum formation time t _n , we note an increase in the interfacial tension γ. In other words, the more the drops form at high frequencies, the less the surfactant has time to adsorb and, therefore, the interfacial tension increases.

At the intersection between zones I and II, there is identified a transition point denoted t _κ which corresponds to the minimum characteristic time necessary for the adsorption of the surfactant at the interface between the two liquids. In other words, the time t _κ is a characteristic value of the surfactant studied, in that it corresponds to the minimum duration necessary for this surfactant to adsorb at the interface between the two liquids. From this embodiment, described immediately above, it is possible to implement a method for screening different surfactants.

For this purpose, two immiscible basic liquids are used, which are flown in the capillaries 2 and 4. Then, they are successively added different surfactants, whose characteristic times t _κ are measured according to the steps described. above. The preferred surfactant (s) correspond (s) in particular to those whose characteristic times are less than the characteristic times of the application. Typically, the characteristic time for the spray additives is of the order of one millisecond, while that of the detergency additives is of the order of one second.

This screening of surfactants can be advantageously carried out in many technical fields, such as detergents, or spray additives. Thus, in the case of detergents, the two liquids that are flowing are for example oil and water, while the surfactants studied are of the sulphonate family, or nonionic surfactants.

The invention achieves the previously mentioned objectives. Indeed, the method for determining the interfacial tension, according to the invention, can be implemented simply and quickly. In addition, the various steps it involves are likely to be performed automatically, for most of them.

In addition, the method of the invention provides access to a wide range of interfacial tension values. In addition, it is possible to vary, very quickly, the nature of the two liquids, which we want to know the interfacial tension.

Finally, the installation according to the invention, allowing the implementation of the above method, is of low cost. Indeed, this installation involves a small number of components, whose structure is simple.

The invention will be illustrated below, in the light of the following embodiment, given purely by way of non-limiting.

Two coaxial capillaries are used, the outer capillary having a diameter of 500 micrometers, while the inner capillary has a diameter of 300 micrometers. In the two capillaries, two non-liquid miscible, namely dodecane as an external liquid, and water as an internal liquid. Their respective viscosities are 1.29 × 10 ^-3 Pa.s and 1.10 ^-3 Pa.s.

Different values of the flow rate of dodecane in the outer capillary are set between 0.001 and 100 microliters / second. For each of these flow rates, the internal flow rate of water is increased, according to the process described above. For low values of internal flow, drops of water are formed in the dodecane and, above an internal transition flow, these drops are transformed into a continuous stream of water in the dodecane. Different internal transition flow rate values are deduced, which are reported on the curve of FIG. 8, where they are represented by squares. From the equations presented above, surface tension values between 30 and 50 mN / m are deduced.

The above procedure is repeated, adding to water and dodecane a surfactant noted A, phosphate ester type marketed by Rhodia, at 2% by weight. This allows to obtain different points, materialized by triangles. The surface tension values identified are between 3 and 6 mN / m.

The above process is then repeated, changing the nature of the surfactant. The one used above is replaced by a mixture of 2% by weight of the same surfactant A, added to 4% by weight of sec-butanol. By implementing the same process as above, different values of transition flow, materialized by diamonds, are obtained. The surface tension values identified are between 0.06 and 0.08 mN / m. Finally, we repeat the same experiment, changing the nature of the surfactant again. Thus a first 50/50 mixture of surfactant A above and a surfactant noted B, different from that A but of a similar nature, is used. 2% by weight of this mixture is added, as well as 4% by weight of sec-butanol. This gives access to different values of transition flow, materialized by circles. The extracted surface tension values are close to 0.008 mN / m.

In FIG. 8, in addition to the experimental points presented above, the different theoretical curves available in the literature are shown. We notes that the experimental points are relatively close to these curves, which makes it possible to check the coherence of the measurements made. If necessary, these experimental curves can be adjusted to deduce one or more surface tension values.

Claims

A method for determining at least one interfacial tension value between two liquids, comprising the steps of:

a first liquid, said internal liquid (U), is flowed into an internal flow member (2), and a second liquid, said external liquid (Le), into an external flow member ( 4), the respectively inner and outer flow members being coaxial, and the inner member opening into the internal volume of the outer flow member;

it is first placed under conditions such that, downstream of the outlet (2 ') of the internal flow member in the external flow member, it is formed,

. i) drops (G) of the internal liquid in a carrier phase (P) formed by the external liquid,

. ii) a continuous jet (J) of the inner liquid in the outer liquid;

the flow rate of at least one of the two liquids is varied;

a pair of liquid flow rate values, referred to as transition values, are identified from which

. i) a continuous stream of the internal liquid is now formed in the external liquid;

. ii) drops of the internal liquid are now formed in the external liquid; and - said value (γ) of interfacial tension between these two liquids is deduced therefrom.

2. Determination method according to claim 1, characterized in that the diameter (Di) of the inner flow member (2) is between 10 micrometers and 2 millimeters, in particular between 10 and 200 micrometers, while the The diameter (De) of the outer flow member (4) is between 50 micrometers and 4 millimeters, preferably between 100 and 500 micrometers.

3. Determination method according to claim 1 or 2, characterized in that the ratio between the diameter of the outer flow member and the The diameter of the inner flow member is between 1, 2 and 10, preferably between 1, 5 and 5.

4. Determination method according to any one of the preceding claims, characterized in that the two liquids (Li, Le) flow at flow rates (Qi, Qe) of between 1 microliter per hour and 100 ml per minute. hour, preferably between 10 and 10,000 microliters per hour.

5. Determination method according to one of the preceding claims, characterized in that the flow rate, said external (Q _e ), of the external liquid is fixed and the flow rate, said internal (Q ₁ ), of the internal liquid is varied. .

6. Determination method according to claim 5, characterized in that the value of the interfacial tension is deduced from the fixed flow rate of the external liquid, the flow rate of the internal liquid, the diameter of the outer capillary, as well as viscosities. indoor and outdoor liquids.

7. Determination method according to claim 6, characterized in that, to deduce this interfacial tension value, the equation is used:

Kax ³ E (x, λ) = CF (x, λ) where

E (x, λ) = -4x + (8 - 4 / T ¹ ) x ³ + 4 (/ T ¹ - 1) x ⁵ , F (x, X) = x ⁴ (4 - / T ¹ + 4 ln) (x)) + x ⁶ (-8 + 4 / T ¹ ) +

Ka = -, with

Y

AP = ¹²⁸ ^ a πD _e ^A (\ -x ² )

8. Determination method according to one of claims 5 to 7, characterized in that several interfacial tension values are determined between the same two liquids, successively fixing different values of external flow (Q _e ) and then for each of these values thus fixed, by varying the values of internal flow (Q ₁ ).

9. Determination method according to any one of the preceding claims, characterized in that a surfactant is added to the two liquids, the time (t) of formation of drops (G) is varied, several values of interfacial tension are determined. between these two same liquids, relating to formation times (ti-t _n ) of different drops, a curve is produced representing the variation of this interfacial tension value as a function of the drop formation time, and a characteristic time is identified. (tk) of the surfactant, corresponding to the transition between a first zone (I) where the interfacial tension value is substantially constant as a function of the drop formation time, and a second zone (II), where this interfacial tension value increases as this training time decreases.

10. Determination method according to any one of the preceding claims, characterized in that it identifies the existence of drops (G) or the existence of a jet (J), by placing a laser emitter (6) and a photodiode (8) on either side of the outer flow member (4), downstream of the outlet (2 ') of the inner flow member (2).

11. Installation for carrying out the method according to any one of the preceding claims, comprising:

- an inner flow member (2) and a coaxial outer flow member (4), the inner flow member opening into the inner volume of the outer flow member;

means for supplying two liquids (Li, Le) respectively in the two flow members;

means for varying the flow rate of at least one of the liquids; and means for observing (6, 8) the flow of the first liquid in the second liquid.

12. A method for screening different pairs of liquid, in which these different pairs of liquid are prepared, determining at least one value of interfacial tension relative to each of these pairs of liquid, according to the method according to one of claims 1 to 10, and at least one preferred pair of liquids is identified among said plurality of pairs of liquid.

13. A screening method according to claim 12, characterized in that the different pairs of liquid are prepared by adding at least one substance to at least one liquid, this substance being in particular a surfactant and / or a polymer and / or a particle. solid.

14. Screening method according to one of claims 12 or 13, characterized in that the different pairs of liquid are prepared by modifying at least one condition of at least one liquid, in particular the pH and / or temperature and / or the pressure.